1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device and to a semiconductor device manufactured thereby, and more particularly, to a cleaning process of a semiconductor substrate.
2. Description of the Background Art
Adsorption and elimination of particles onto and from the surface of a semiconductor substrate are usually explained by an electrostatic phenomenon. When the surface of the semiconductor substrate and the surfaces of particles are charged with the same polarity, particles leave from the surface of the semiconductor substrate by electrostatic repulsion. In an alkaline cleaning fluid, the surface of the semiconductor substrate and the surfaces of particles are charged with the same polarity.
Accordingly, in the course of manufacture of a semiconductor device, an alkaline cleaning fluid; for example aqueous ammonium hydroxide or a mixed hydrogen peroxide liquid (hereinafter called xe2x80x9cAPMxe2x80x9d), has been widely used for a process of cleaning a semiconductor substrate.
Tungsten used as material of a wire has the property of reacting vigorously with an oxidizing agent such as hydrogen peroxide until dissolution. For this reason, a semiconductor substrate having tungsten exposed thereon cannot be cleaned by use of APM.
A solution of hydroxide has been used as a cleaning fluid in the process of cleaning a semiconductor substrate having tungsten or an alloy thereof (hereinafter called xe2x80x9ctungsten-based membersxe2x80x9d) exposed thereon.
Here, the hydroxides include ammonium hydroxide, sodium hydroxide, potassium hydroxide, and tetramethylammonium hydroxide (hereinafter called xe2x80x9cTMAHxe2x80x9d). From the viewpoint of protection of a semiconductor substrate from metal contamination, use of ammonium hydroxide or TMAH, which does not contain any metal atoms, is preferable in cleaning the semiconductor substrate.
Since a solution of ammonium hydroxide (hereinafter called xe2x80x9caqueous ammoniumxe2x80x9d) has the property of dissolving silicon, aqueous ammonium cannot be used for cleaning a semiconductor substrate having exposed thereon a silicon-based member such as polycrystalline silicon (hereinafter called xe2x80x9cpolysiliconxe2x80x9d), amorphous silicon, a silicon oxide film, or a silicon substrate.
For these reasons, the alkaline cleaning fluid cannot be used for cleaning a semiconductor substrate having both a tungsten-based member and a silicon-based member exposed thereon.
In order to clean the semiconductor substrate having exposed the tungsten-based member and exposed the silicon-based member, a compound expressed by the following chemical formula (I) or (II), which is served as a silicon corrosion inhibitor, is added to the cleaning fluid containing an aqueous hydroxide, or an aqueous ammonium, for example.
HO-{(EO)x-(PO)y}z-Hxe2x80x83xe2x80x83(I)
R-[{(EO)x-(PO)y}z-H]mxe2x80x83xe2x80x83(II)
wherein xe2x80x9cEOxe2x80x9d designates an oxyethyethylene group, and xe2x80x9cPOxe2x80x9d designates an oxypropylene group. xe2x80x9cRxe2x80x9d designates a residue formed by eliminating hydrogen atoms from a hydroxyl group of alcohol or amine, or a residue formed by eliminating hydrogen atoms from an amino acid. xe2x80x9cxxe2x80x9d and xe2x80x9cyxe2x80x9d are integers satisfying x/(x+y)=0.05 to 0.4, and xe2x80x9czxe2x80x9d and xe2x80x9cmxe2x80x9d are positive integers.
Next, a conventional method of manufacturing a semiconductor device using the foregoing cleaning fluid will be described.
With reference to FIGS. 1A to 1C, a first conventional method of manufacturing a semiconductor device will be described. More specifically, a method of forming a gate electrode of a MOS transistor will be described.
As shown in FIG. 1A, a gate insulating film 2, a polysilicon film 11, a barrier metal layer 21, and a tungsten film 31 are formed on a semiconductor substrate 1, in the sequence.
Next, as shown in FIG. 1B, a resist pattern 51 is formed on the tungsten film 31, and an interconnection pattern (gate electrode) 41 is formed by dry etching with the resist pattern 51 as a mask.
Next, as shown in FIG. 1C, the resist pattern 51 is removed by plasma ashing (ashing), thereafter resist residues 61 are remained on the top of the gate electrode 41. Although not shown, the resist residues 61 are remained on the both sides of the gate electrode 41.
Finally, the semiconductor substrate is cleaned in a subsequent cleaning step, in which the semiconductor substrate 1 is cleaned by use of the previously-described cleaning fluid. Thus, the resist residues 61 are removed from the semiconductor substrate 1, and a semiconductor device is manufactured.
With reference to FIGS. 2A to 2C, a second conventional method of manufacturing a semiconductor device will be described. More specifically, a method of forming a source region and a drain region of a MOS transistor will be described.
With reference to FIG. 2A, the interconnection pattern (gate electrode) 41 is formed on the gate insulating film 2 formed on the semiconductor substrate 1, by the same method as that illustrated in FIGS. 1A to 1C.
Further, a resist pattern 52 is formed on the gate electrode 41 and on the gate insulating film 2 around the gate electrode 41.
Next, ions are implanted into the semiconductor substrate 1 (as indicated by arrows shown in FIG. 2A) with the resist pattern 52 as a mask. Thus, although not shown, a source region or a drain region of a MOS transistor is formed in the semiconductor substrate 1.
Subsequently, although not shown, the resist pattern 52 is removed by plasma ashing, thereafter resist residues 62 are remained on the gate insulating film 2 on the semiconductor substrate 1, as shown in FIG. 2B.
Finally, although not shown, the semiconductor substrate 1 is cleaned in cleaning step, more specifically, in which the semiconductor substrate 1 is cleaned by use of the previously-described cleaning fluid. Thus, the resist residues 62 are removed from the semiconductor substrate 1, and the semiconductor device is manufactured.
As shown in FIG. 2C, there may be a case in which, after side walls 71 have been formed on the both sides of the gate electrode 41, ions are implanted into the semiconductor substrate 1. Even in such a case, a silicon-based member or a tungsten-based member may become partially exposed through pin holes formed in the side walls 71. For this reason, the semiconductor substrate 1 is cleaned by use of the previously-described cleaning fluid, to thereby remove the resist residues 63.
In the cleaning step of the conventional methods, however, there are problems as follows.
In a case where the cleaning fluid has a high hydroxide content, the silicon inhibitor cannot be added to the cleaning fluid at high concentration. The reason for this is that, if both the silicon corrosion inhibitor and hydroxide are added to the cleaning fluid at high concentrations, the cleaning capability of the cleaning fluid is resultant degraded.
More specifically, in the cleaning step of the semiconductor substrate having a silicon-based member and a tungsten-based member exposed thereon, use of the cleaning fluid cannot be attained both a high cleaning capability and a high silicon corrosion prevention effect simultaneously.
In order to remove particles from the semiconductor substrate 1, the previously-described cleaning step is often carried out several times.
Further, in a case where plural transistors having different electrical properties are formed on the semiconductor substrate 1, the steps illustrated in FIGS. 2A to 2C (i.e., the step of forming a resist pattern, the step of implanting ions, the step of removing a resist pattern, and a cleaning step) must be carried out several times.
Here, a hydroxide, which is contained in the cleaning fluid, has the property of eluting tungsten slightly.
Therefore, in the case that the semiconductor substrate 1 must be cleaned several times as mentioned above, an amount, to which the tungsten film 31 is eluted by use of the previously-described cleaning fluid, exceeds an allowable range. As a result, which may cause formation of the interconnection pattern 41 having an abnormal shape, or deterioration of electrical characteristic of a transistor.
The present invention has been conceived to solve the previously-mentioned problems and a general object of the present invention is to provide a novel and useful method of manufacturing a semiconductor device, and semiconductor device.
A more specific object of the present invention is to attain a high cleaning capability and a high silicon corrosion prevention effect simultaneously in a cleaning step of a semiconductor substrate having tungsten and silicon exposed thereon.
A more specific another object of the present invention is to attain a high tungsten corrosion prevention effect in a cleaning step of the method of manufacturing a semiconductor device.
The above object of the present invention is attained by a following method of manufacturing a semiconductor device.
According to one aspect of the present invention, in a method of manufacturing a semiconductor device, a semiconductor substrate is cleaned by use of a cleaning fluid containing a hydroxide, a water-soluble organic solvent, and a compound expressed by the following chemical formula (I) or (II), in a cleaning step.
HO-{(EO)x-(PO)y}z-Hxe2x80x83xe2x80x83(I)
R-[{(EO)x-(PO)y}z-H]mxe2x80x83xe2x80x83(II)
wherein xe2x80x9cEOxe2x80x9d designates an oxyethyethylene group; xe2x80x9cPOxe2x80x9d designates an oxypropylene group; xe2x80x9cRxe2x80x9d designates a residue formed by eliminating hydrogen atoms from a hydroxyl group of alcohol or amine, or a residue formed by eliminating hydrogen atoms from an amino acid; xe2x80x9cxxe2x80x9d and xe2x80x9cyxe2x80x9d are integers satisfying x/(x+y)=0.05 to 0.4; and xe2x80x9czxe2x80x9d and xe2x80x9cmxe2x80x9d are positive integers.
In the method of manufacturing a semiconductor device, the cleaning fluid containing the water-soluble organic solvent which increase a concentration of a hydroxide, the compound which is expressed by the chemical formula (I) or (II) and is served as a silicon corrosion inhibitor, is used in the cleaning step. Therefore, a high cleaning capability and a high silicon corrosion prevention effect is attained simultaneously in the cleaning step.
According to another aspect of the present invention, in a manufacturing method of a semiconductor device, a semiconductor substrate is cleaned by use of a cleaning fluid containing a hydroxide, and at least one organic compound selected from the group of the an organic compound having at least one mercapto group, an organic compound having at least two hydroxyl groups, and an organic compound having at least one hydroxyl group and at least one carboxyl group, in a cleaning step.
In the method of manufacturing a semiconductor device, the cleaning fluid containing the organic compound, which is served as a tungsten corrosion inhibitor, is used in the cleaning step. Therefore, a high tungsten corrosion prevention effect is attained in the cleaning step.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.